U.S. patent number 8,457,742 [Application Number 11/549,599] was granted by the patent office on 2013-06-04 for leadless cardiac pacemaker system for usage in combination with an implantable cardioverter-defibrillator.
This patent grant is currently assigned to Nanostim, Inc.. The grantee listed for this patent is Peter M. Jacobson. Invention is credited to Peter M. Jacobson.
United States Patent |
8,457,742 |
Jacobson |
June 4, 2013 |
Leadless cardiac pacemaker system for usage in combination with an
implantable cardioverter-defibrillator
Abstract
A cardiac pacing system comprising one or more leadless cardiac
pacemakers configured for implantation in electrical contact with a
cardiac chamber and configured to perform cardiac pacing functions
in combination with a co-implanted implantable
cardioverter-defibrillator (ICD). The leadless cardiac pacemaker
comprises at least two leadless electrodes configured for
delivering cardiac pacing pulses, sensing evoked and/or natural
cardiac electrical signals, and bidirectionally communicating with
the co-implanted ICD.
Inventors: |
Jacobson; Peter M. (Chanhassen,
MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Jacobson; Peter M. |
Chanhassen |
MN |
US |
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Assignee: |
Nanostim, Inc. (Sunnyvale,
CA)
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Family
ID: |
37963216 |
Appl.
No.: |
11/549,599 |
Filed: |
October 13, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070088394 A1 |
Apr 19, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60726706 |
Oct 14, 2005 |
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60729671 |
Oct 24, 2005 |
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60737296 |
Nov 16, 2005 |
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60739901 |
Nov 26, 2005 |
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60749017 |
Dec 10, 2005 |
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60761531 |
Jan 24, 2006 |
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60761740 |
Jan 24, 2006 |
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Current U.S.
Class: |
607/33;
607/2 |
Current CPC
Class: |
A61N
1/3956 (20130101); A61N 1/0573 (20130101); A61N
1/3627 (20130101); A61N 1/3727 (20130101); A61N
1/3621 (20130101); A61N 1/056 (20130101); A61N
1/37205 (20130101); H04B 13/005 (20130101); A61N
1/3684 (20130101); A61N 1/372 (20130101); A61N
1/37252 (20130101); A61N 1/39622 (20170801); A61N
1/0587 (20130101); A61N 1/3708 (20130101); A61N
1/3756 (20130101); A61N 1/36842 (20170801); A61N
1/3704 (20130101); A61N 1/3706 (20130101); A61N
1/368 (20130101); A61N 1/37217 (20130101); A61N
1/37512 (20170801); A61N 1/059 (20130101); A61N
1/37288 (20130101); A61N 1/3925 (20130101); A61N
1/36514 (20130101); A61M 25/0662 (20130101); A61N
2001/058 (20130101); A61N 1/36542 (20130101); A61N
1/37518 (20170801) |
Current International
Class: |
A61N
1/05 (20060101) |
Field of
Search: |
;600/508-509
;607/2-9,33,36-37 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1741465 |
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Jan 2007 |
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EP |
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05-245215 |
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Sep 1993 |
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JP |
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06/507096 |
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Mar 2006 |
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JP |
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06/516449 |
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Jul 2006 |
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JP |
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WO93/12714 |
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Jul 1993 |
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WO |
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WO 98/37926 |
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Sep 1998 |
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WO |
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WO2004/012811 |
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Feb 2004 |
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WO |
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WO 2006/065394 |
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Jun 2006 |
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WO |
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WO 2007/047681 |
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Apr 2007 |
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WO |
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WO 2007/059386 |
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May 2007 |
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WO |
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Other References
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applicant .
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of US Patent No. 7,630,767 B1, Dec. 8, 2009). cited by applicant
.
Jacobson, Peter M.; U.S. Appl. No. 12/953,282 entitled "Leadless
Cardiac Pacemaker Triggered by Conductive Communication," filed
Nov. 23, 2010. cited by applicant .
Beeby et al.; Micromachined silicon generator for harvesting power
from vibrations; (Proceedings) PowerMEMS 2004; Kyoto, Japan; pp.
104-107; Nov. 28-30, 2004. cited by applicant .
Brown, Eric S.; The atomic battery; Technology Review: Published by
MIT; 4 pgs.; Jun. 16, 2005. cited by applicant .
Irnich et al.; Do we need pacemakers resistant to magnetic
resonance imaging; Europace; vol. 7; pp. 353-365; 2005. cited by
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Irnich; Electronic security systems and active implantable medical
devices; Journal of PACE; vol. 25; No. 8; pp. 1235-1258; Aug. 2002.
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Luchinger ; Safety aspects of cardiac pacemakers in magnetic
resonance imaging; Dissertation submitted to the Swiss Federal
Institute of Technology Zurich; 2002. cited by applicant .
Nyenhuis et al.; MRI and Implanted Medical Devices: Basic
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Leadless Cardiac Pacemaker," Sep. 28, 2009. cited by applicant
.
Ostroff, Alan; U.S. Appl. No. 12/698,969 entitled "Leadless Cardiac
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cited by applicant .
Jacobson, Peter M.; U.S. Appl. No. 13/191,229 entitled "Implantable
biostimulator delivery system," filed Jul. 26, 2011. cited by
applicant .
Khairkhahan et al.; U.S. Appl. No. 13/272,074 entitled "Delivery
catheter systems and methods," filed Oct. 12, 2011. cited by
applicant .
Khairkhahan et al.; U.S. Appl. No. 13/272,082 entitled "Leadless
cardiac pacemaker with anti-unscrewing feature," filed Oct. 12,
2011. cited by applicant .
Ostroff, Alan; U.S. Appl. No. 13/272,092 entitled "Temperature
sensor for a leadless cardiac pacemaker," filed Oct. 12, 2011.
cited by applicant .
Khairkhaha et al.; U.S. Appl. No. 13/324,781 entitled "Delivery
Catheter Systems and Methods," filed Dec. 13, 2011. cited by
applicant .
Jacobson et al.; U.S. Appl. No. 13/277,151 entitled "Leadless
cardiac pacemaker with conducted communication," filed Oct. 19,
2011. cited by applicant .
Khairkhahan et al.; U.S. Appl. No. 13/324,802 entitled "Pacemaker
Retrieval Systems and Methods ," filed Dec. 13, 2011. cited by
applicant .
Khairkhahan et al.; U.S. Appl. No. 13/331,922 entitled "Leadless
Pacemaker with Radial Fixation Mechanism ," filed Dec. 20, 2011.
cited by applicant .
Bordacher et al.; Impact and prevention of far-field sensing in
fallback mode switches; PACE; vol. 26 (pt. II); pp. 206-209; Jan.
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Primary Examiner: Holmes; Rex R
Attorney, Agent or Firm: Shay Glenn LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority to and incorporates
herein by reference in its entirety for all purposes, Provisional
U.S. Patent Application Nos. 60/726,706 entitled "LEADLESS CARDIAC
PACEMAKER WITH CONDUCTED COMMUNICATION," filed Oct. 14, 2005;
60/761,531 entitled "LEADLESS CARDIAC PACEMAKER DELIVERY SYSTEM,"
filed Jan. 24, 2006; 60/729,671 entitled "LEADLESS CARDIAC
PACEMAKER TRIGGERED BY CONDUCTED COMMUNICATION," filed Oct. 24,
2005; 60/737,296 entitled "SYSTEM OF LEADLESS CARDIAC PACEMAKERS
WITH CONDUCTED COMMUNICATION," filed Nov. 16, 2005; 60/739,901
entitled "LEADLESS CARDIAC PACEMAKERS WITH CONDUCTED COMMUNICATION
FOR USE WITH AN IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR," filed Nov.
26, 2005; 60/749,017 entitled "LEADLESS CARDIAC PACEMAKER WITH
CONDUCTED COMMUNICATION AND RATE RESPONSIVE PACING," filed Dec. 10,
2005; and 60/761,740 entitled "PROGRAMMER FOR A SYSTEM OF LEADLESS
CARDIAC PACEMAKERS WITH CONDUCTED COMMUNICATION," filed Jan. 24,
2006; all by Peter M. Jacobson.
Claims
What is claimed is:
1. A cardiac pacing system comprising: at least one leadless
cardiac pacemaker configured for implantation in electrical contact
with a cardiac chamber and configured to perform cardiac pacing
functions in combination with a co-implanted implantable
cardioverter-defibrillator (ICD), the at least one leadless cardiac
pacemaker comprising a pulse generator configured to generate
pulses adapted to perform cardiac pacing and pulses encoding
information for transmission as communication signals, and at least
two electrodes configured to deliver generated pulses, sense evoked
and/or natural cardiac electrical signals, and bidirectionally
communicate with a non-implanted programmer by operation of the
pulse generator to encode and transmit generated pulses operative
as communication signals, the at least one leadless cardiac
pacemaker configured to intercommunicate and directly communicate
with a non-implanted programmer via pulses generated by the pulse
generator and encoded into communication signals wherein
transmitted communication power requirements are essentially met by
power consumed in cardiac pacing.
2. The system according to claim 1 further comprising: the at least
one leadless cardiac pacemaker configured to intercommunicate and
directly communicate with a non-implanted programmer and the
implanted ICD by transmitting pulses generated by the pulse
generator and encoded to be operative as communication signals via
the at least two electrodes that are also used for delivering
pacing pulses.
3. A system according to claim 1 further comprising: the at least
one leadless cardiac pacemaker comprising: a hermetic housing
configured for placement on or attachment to the inside or outside
of a cardiac chamber; and the at least two electrodes proximal to
the housing that bidirectional communicates directly with at least
one other device within or outside the body.
4. The system according to claim 1 further comprising: the at least
one leadless cardiac pacemaker configured to communicate
bidirectionally among a plurality of leadless cardiac pacemakers
and the implanted ICD to coordinate pacing pulse delivery via
pulses generated by the pulse generator and encoded into
communication signal messages that identify an event at an
individual pacemaker originating the message and pacemakers
receiving the message react as directed by the message depending on
the message origin.
5. The system according to claim 1 further comprising: the at least
one leadless cardiac pacemaker configured to communicate
bidirectionally via pulses generated by the pulse generator and
encoded into communication signals among a plurality of leadless
cardiac pacemakers and the implanted ICD to facilitate sensitivity
and specificity of the ICD.
6. The system according to claim 1 further comprising: the at least
one leadless cardiac pacemaker configured to communicate via pulses
generated by the pulse generator and encoded into communication
signals with a subcutaneous-only implantable defibrillator to
improve sensitivity and specificity of the subcutaneous-only
implantable defibrillator whereby atrial depolarization and
ventricular depolarization are uniquely and specifically
identified.
7. The system according to claim 1 further comprising: the at least
two electrodes configured to communicate bidirectionally via pulses
generated by the pulse generator and encoded into communication
signals among a plurality of leadless cardiac pacemakers and the
ICD and convey data including designated codes for events detected
or created by an individual pacemaker, the individual pacemakers
issuing a unique code corresponding to an event type and a location
of the individual pacemaker.
8. The system according to claim 1 further comprising: individual
pacemakers of a plurality of leadless cardiac pacemakers configured
to deliver at least one pulse generated by the pulse generator and
encoded into a code assigned according to pacemaker location and
transmit a message to at least one pacemaker of the plurality of
leadless cardiac pacemakers via the at least one pulse wherein the
code identifies the individual pacemaker originating an event, the
at least one pacemaker receiving the message being responsive to
the message in a predetermined manner depending on type and
location of the event.
9. The system according to claim 1 further comprising: individual
pacemakers a plurality of leadless cardiac pacemakers configured to
deliver at least one pulse generated by the pulse generator and
encoded into a code assigned according to pacemaker location and
transmit a message to at least one pacemaker of the plurality of
leadless cardiac pacemakers via the at least one pulse wherein the
code identifies the individual pacemaker originating an event, the
individual pacemakers further delivering a pacing pulse in absence
of encoding whereby, for dual-chamber cardiac pacing, a pacing
pulse that is not generated in a first cardiac pacemaker that
senses the pacing pulse is necessarily generated in a second
cardiac pacemaker.
10. The system according to claim 1 further comprising: individual
pacemakers of a plurality of leadless cardiac pacemakers configured
to convey to at least one pacemaker of the plurality of leadless
cardiac pacemakers at least one pulse generated by the pulse
generator and encoded into a signal indicating occurrence of a
sensed heartbeat at the individual pacemaker location via
generation of at least one pulse triggered by the sensed heartbeat
in a natural refractory period following the sensed heartbeat.
11. The system according to claim 1 further comprising: individual
pacemakers of the plurality of leadless cardiac pacemakers
configured to receive conducted communication from a co-implanted
cardioverter-defibrillator (ICD) that configures the individual
pacemakers to deliver overdrive anti-tachycardia pacing in response
to a detected tachyarrhythmia.
12. The system according to claim 1 further comprising: individual
pacemakers of the plurality of leadless cardiac pacemakers
configured for operation in a particular location and a particular
functionality at manufacture and/or at programming by an external
programmer.
13. The system according to claim 1 further comprising: the
plurality of leadless cardiac pacemakers comprising a right
ventricular leadless cardiac pacemaker and a left ventricular
leadless cardiac pacemaker configured to operate with
atrio-ventricular (AV) delays wherein a left ventricular pacing
pulse can be delivered before, after, or substantially
simultaneously with a right ventricular pacing pulse.
14. The system according to claim 13 further comprising: the
right-ventricular leadless cardiac pacemaker configured to: set
ventricular-to-ventricular (VV) escape interval longer than a
predetermined atrial-to-atrial (AA) escape interval to enable
backup ventricular pacing at a low rate corresponding to the VV
escape interval in case of failure of a triggered signal from a
co-implanted atrial leadless cardiac pacemaker.
15. The system according to claim 1 further comprising: the at
least two electrodes configured to communicate bidirectionally
among the plurality of leadless cardiac pacemakers and transmit
pulses generated by the pulse generator and encoded into data
including designated codes for events detected or created by an
individual pacemaker, the codes encoding information using a
technique selected from a group consisting of encoding in pacing
pulse width, encoding in binary-coded notches in a pacing pulse,
encoding as modulation of off-time between pacing pulses, and
encoding of multiple pulses comprising absence and presence of
pulses and time between pulses including refractory and/or
subliminal pulses.
16. The system according to claim 1 further comprising: an atrial
leadless cardiac pacemaker further configured to: time a prolonged
post-ventricular atrial refractory period (PVARP) after recycling
in presence of the premature signal whereby pacemaker-mediated
tachycardia is prevented.
17. The system according to claim 1 further comprising: an
implanted cardioverter-defibrillator (ICD) comprising a case and
pair of electrodes mounted on or near the case, the ICD configured
to receive and transmit conducted communication using a pulse
modulated or frequency modulated signal wherein the ICD detects
communication pulses from co-implanted leadless cardiac pacemakers
and transmits information to the co-implanted leadless cardiac
pacemakers.
18. The system according to claim 1 further comprising: an
implanted cardioverter-defibrillator (ICD) configured to receive
conducted communication using at least two implantable
electrodes.
19. The system according to claim 1 further comprising: individual
pacemakers of the plurality of leadless cardiac pacemakers
comprising: a receiving amplifier/filter adapted for multiple
controllable gain settings; and a processor configured to control
gain setting for the receiving amplifier/filter, invoke a low-gain
setting for normal operation and detect presence of at least one
pulse, and, invoke a high-gain setting for detecting information
encoded in the at least one pulse.
20. The system according to claim 1 further comprising: individual
pacemakers of the plurality of leadless cardiac pacemakers
comprising: a tank capacitor switched across a pair of the at least
two electrodes and adapted for charging and discharging wherein a
pacing pulse is generated; a charge pump circuit coupled to the
tank capacitor and adapted for controlling charging of the tank
capacitor; and a processor that controls recharging of the tank
capacitor wherein recharging is discontinued when a battery
terminal voltage falls below a predetermined value to ensure
sufficient voltage for powering the leadless cardiac pacemaker.
Description
BACKGROUND
Cardiac pacing electrically stimulates the heart when the heart's
natural pacemaker and/or conduction system fails to provide
synchronized atrial and ventricular contractions at appropriate
rates and intervals for a patient's needs. Such bradycardia pacing
provides relief from symptoms and even life support for hundreds of
thousands of patients. Cardiac pacing may also give electrical
overdrive stimulation intended to suppress or convert
tachyarrhythmias, again supplying relief from symptoms and
preventing or terminating arrhythmias that could lead to sudden
cardiac death.
Cardiac pacing is usually performed by a pulse generator implanted
subcutaneously or sub-muscularly in or near a patient's pectoral
region. Implantable cardioverter-defibrillator (ICD) pulse
generators usually include cardiac pacing functions, both for
bradycardia support and for overdrive stimulation. The generator
usually connects to the proximal end of one or more implanted
leads, the distal end of which contains one or more electrodes for
positioning adjacent to the inside or outside wall of a cardiac
chamber. The leads have an insulated electrical conductor or
conductors for connecting the pulse generator to electrodes in the
heart. Such electrode leads typically have lengths of 50 to 70
centimeters.
A conventional pulse generator may be connected to more than one
electrode-lead. For example, atrio-ventricular pacing, also
commonly called dual-chamber pacing, involves a single pulse
generator connected to one electrode-lead usually placed in the
right atrium and a second electrode-lead usually placed in the
right ventricle. Such a system can electrically sense heartbeat
signals and deliver pacing pulses separately in each chamber. In
typical use, the dual-chamber pacing system paces the atrium if no
atrial heartbeat is sensed since a predetermined time, and then
paces the ventricle if no ventricular heartbeat is sensed within a
predetermined time after the natural or paced atrial beat. Such
pulse generators can also alter the timing of atrial and
ventricular pacing pulses when sensing a ventricular beat that is
not preceded by an atrial beat within a predetermined time; that
is, a ventricular ectopic beat or premature ventricular
contraction. Consequently, dual-chamber pacing involves pacing and
sensing in an atrium and a ventricle, and internal communication
element so that an event in either chamber can affect timing of
pacing pulses in the other chamber.
Recently, left-ventricular cardiac pacing has been practiced to
ameliorate heart failure; a practice termed cardiac
resynchronization therapy (CRT). CRT has been practiced with
electrode-leads and a pulse generator, either an implantable
cardioverter-defibrillator (CRT-D) or an otherwise conventional
pacemaker (CRT-P). The left-ventricular pacing conventionally uses
an electrode in contact with cardiac muscle in that chamber. The
corresponding electrode-lead is usually placed endocardially in a
transvenous manner through the coronary sinus vein, or
epicardially. Left-ventricular pacing is usually practiced together
with right-atrial and right-ventricular pacing with a single
implanted pulse generator connected to three electrode-leads. CRT
pulse generators can independently vary the time between an atrial
event and right-ventricular pacing, and the time between an atrial
event and left-ventricular pacing, so that the left ventricular
pacing pulse can precede, follow, or occur at the same time as the
right-ventricular pacing pulse. Similarly to dual-chamber pacing,
systems with left-ventricular pacing also change atrial and
ventricular pacing timing in response to premature ventricular
contractions. Consequently, CRT-D involves pacing in an atrium and
in two ventricles, sensing in the atrium and at least one
ventricle, and an internal communication element so that an event
in the atrium can affect timing of pacing pulses in each ventricle,
and an internal communication element so that an event in at least
one ventricle can affect timing of pacing pulses in the atrium and
the other ventricle.
Pulse generator parameters are usually interrogated and modified by
a programming device outside the body, via a loosely-coupled
transformer with one inductance within the body and another
outside, or via electromagnetic radiation with one antenna within
the body and another outside.
Although more than one hundred thousand ICD and CRT-D systems are
implanted annually, several problems are known.
A conventional pulse generator has an interface for connection to
and disconnection from the electrode leads that carry signals to
and from the heart. Usually at least one male connector molding has
at least one additional terminal pin not required for
defibrillation functions at the proximal end of the electrode lead.
The at least one male connector mates with at least one
corresponding female connector molding and terminal block within
the connector molding at the pulse generator. Usually a setscrew is
threaded in at least one terminal block per electrode lead to
secure the connection electrically and mechanically. One or more
O-rings usually are also supplied to help maintain electrical
isolation between the connector moldings. A setscrew cap or slotted
cover is typically included to provide electrical insulation of the
setscrew. The complex connection between connectors and leads
provides multiple opportunities for malfunction.
For example, failure to introduce the lead pin completely into the
terminal block can prevent proper connection between the generator
and electrode.
Failure to insert a screwdriver correctly through the setscrew
slot, causing damage to the slot and subsequent insulation
failure.
Failure to engage the screwdriver correctly in the setscrew can
cause damage to the setscrew and preventing proper connection.
Failure to tighten the setscrew adequately also can prevent proper
connection between the generator and electrode, however
over-tightening of the setscrew can cause damage to the setscrew,
terminal block, or lead pin, and prevent disconnection if necessary
for maintenance.
Fluid leakage between the lead and generator connector moldings, or
at the setscrew cover, can prevent proper electrical isolation.
Insulation or conductor breakage at a mechanical stress
concentration point where the lead leaves the generator can also
cause failure.
Inadvertent mechanical damage to the attachment of the connector
molding to the generator can result in leakage or even detachment
of the molding.
Inadvertent mechanical damage to the attachment of the connector
molding to the lead body, or of the terminal pin to the lead
conductor, can result in leakage, an open-circuit condition, or
even detachment of the terminal pin and/or molding.
The lead body can be cut inadvertently during surgery by a tool, or
cut after surgery by repeated stress on a ligature used to hold the
lead body in position. Repeated movement for hundreds of millions
of cardiac cycles can cause lead conductor breakage or insulation
damage anywhere along the lead body.
Although leads are available commercially in various lengths, in
some conditions excess lead length in a patient exists and is to be
managed. Usually the excess lead is coiled near the pulse
generator. Repeated abrasion between the lead body and the
generator due to lead coiling can result in insulation damage to
the lead.
Friction of the lead against the clavicle and the first rib, known
as subclavian crush, can result in damage to the lead.
In dual-chamber pacing in an ICD, and in CRT-D, multiple leads are
implanted in the same patient and sometimes in the same vessel.
Abrasion between these leads for hundreds of millions of cardiac
cycles can cause insulation breakdown or even conductor
failure.
Subcutaneous ICDs that do not use endocardial, transvenous or
epicardial lead wires, can deliver defibrillation using
subcutaneous electrodes. However, pacing the heart from
subcutaneous electrodes results in diaphragmatic stimulation which
is uncomfortable to the patient if used in long-term therapy.
Therefore pacing therapies such as bradycardia pacing therapy,
anti-tachycardia therapy, atrial overdrive pacing for the
prevention of arrhythmias, dual chamber pacing for
atrio-ventricular synchronization and CRT therapies are
inappropriate.
SUMMARY
According to an embodiment of a cardiac pacing system, one or more
leadless cardiac pacemakers are configured for implantation in
electrical contact with a cardiac chamber and configured for
performing cardiac pacing functions in combination with a
co-implanted implantable cardioverter-defibrillator (ICD). The
leadless cardiac pacemaker comprises at least two leadless
electrodes configured for delivering cardiac pacing pulses, sensing
evoked and/or natural cardiac electrical signals, and
bidirectionally communicating with the co-implanted ICD.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention relating to both structure and method
of operation may best be understood by referring to the following
description and accompanying drawings, in which similar reference
characters denote similar elements throughout the several
views:
FIG. 1A is a pictorial diagram showing an embodiment of a cardiac
pacing system including one or more leadless cardiac pacemakers
with conducted communication for performing cardiac pacing in
conjunction with an implantable cardioverter-defibrillator
(ICD);
FIG. 1B is a schematic block diagram showing interconnection of
operating elements of an embodiment of a leadless cardiac pacemaker
that can be used in cardiac pacing system including one or more
leadless cardiac pacemakers and an implantable
cardioverter-defibrillator (ICD);
FIG. 2 is a pictorial diagram showing the physical location of some
elements of an embodiment of a leadless biostimulator that can be
used as part of a multi-chamber cardiac pacing system;
FIG. 3 is a pictorial diagram that depicts the physical location of
some elements in an alternative embodiment of a leadless
biostimulator that can be used as part of a multi-chamber cardiac
pacing system;
FIG. 4 is a time waveform graph illustrating a conventional pacing
pulse;
FIG. 5 is a time waveform graph depicting a pacing pulse adapted
for communication as implemented for an embodiment of the
illustrative pacing system;
FIG. 6 is a time waveform graph showing a sample pulse waveform
using off-time variation for communication;
FIG. 7 is a state-mechanical representation illustrating an
embodiment of a technique for operation of an atrial leadless
cardiac pacemaker in a multi-chamber cardiac pacing system;
FIG. 8 is a state-mechanical representation illustrating an
embodiment of a technique for operation of a right-ventricular
leadless cardiac pacemaker in a multi-chamber cardiac pacing
system;
FIG. 9 is a state-mechanical representation illustrating an
embodiment of a technique for operation of a left-ventricular
leadless cardiac pacemaker in a multi-chamber cardiac pacing
system;
FIGS. 10A and 10B are schematic flow charts that depict embodiments
of methods for operating an atrial leadless cardiac pacemaker in a
cardiac pacing system including an implantable
cardioverter-defibrillator (ICD) and one or more leadless cardiac
pacemakers;
FIGS. 11A and 11B are schematic flow charts that depict embodiments
of methods for operating a right-ventricular leadless cardiac
pacemaker in a cardiac pacing system including an implantable
cardioverter-defibrillator (ICD) and one or more leadless cardiac
pacemakers; and
FIGS. 12A and 12B are schematic flow charts that depict embodiments
of methods for operating a left-ventricular leadless cardiac
pacemaker in a cardiac pacing system including an implantable
cardioverter-defibrillator (ICD) and one or more leadless cardiac
pacemakers.
DETAILED DESCRIPTION
In some embodiments of an illustrative cardiac pacing system, one
or more leadless cardiac pacemakers with low-power conducted
communication can perform single-chamber pacing, dual-chamber
pacing, CRT-D, or other pacing, co-implanted with an ICD, enabling
functionality extending beyond what is possible or appropriate for
conventional subcutaneous ICDs.
A system of leadless cardiac pacemakers enables pacing in
conjunction with an implantable cardioverter-defibrillator (ICD)
for usage in single-chamber, dual-chamber, CRT-D, and other
multi-chamber cardiac pacing schemes.
Various embodiments of a system of an implantable
cardioverter-defibrillator (ICD) and one or more leadless cardiac
pacemakers are described. The individual leadless cardiac
pacemakers can be substantially enclosed in a hermetic housing
suitable for placement on or attachment to the inside or outside of
a cardiac chamber. The pacemaker can have at least two electrodes
located within, on, or near the housing, for delivering pacing
pulses to and sensing electrical activity from the muscle of the
cardiac chamber, and for bidirectional communication with at least
one other co-implanted leadless cardiac pacemaker and optionally
with another device outside the body. The housing can contain a
primary battery to provide power for pacing, sensing, and
communication. The housing can also contain circuits for sensing
cardiac activity from the electrodes, receiving information from at
least one other device via the electrodes, generating pacing pulses
for delivery via the electrodes, transmitting information to at
least one other device via the electrodes, monitoring device
health, and controlling these operations in a predetermined
manner.
A cardiac pacing system includes cardiac pacing in conjunction with
an ICD and can supplement the functionality of ICDs with cardiac
pacing functions, extending beyond functionality of conventional
ICD-pacing arrangements.
The cardiac pacing system comprises a leadless cardiac pacemaker or
pacemakers adapted to perform cardiac pacing functions with a
co-implanted ICD, without a pacing electrode-lead separate from the
leadless cardiac pacemaker, without a communication coil or antenna
in the leadless cardiac pacemaker, and without an additional
requirement on battery power in the leadless cardiac pacemaker for
transmitted communication.
In some embodiments, a cardiac pacing system comprises an ICD with
one or more leadless pacemakers for implantation adjacent to the
inside or outside wall of a cardiac chamber, without the need for a
connection between the leadless pulse generator and an electrode
lead that can be connected or disconnected during implantation and
repair procedures, and without the need for a lead body.
In some embodiments of a cardiac pacing system, communication
between the implanted leadless cardiac pacemaker or pacemakers and
other devices, including any co-implanted leadless cardiac
pacemakers, the co-implanted ICD, and optionally a device external
to the body, uses conducted communication via the same electrodes
used for pacing, without the need for an antenna or telemetry
coil.
Some embodiments and/or arrangements can implement communication
between an implanted leadless cardiac pacemaker and other devices
with power requirements similar to those for cardiac pacing, to
enable optimization of battery performance. For example,
transmission from the leadless cardiac pacemaker adds no power
while reception adds a limited amount of power, such as about 25
microwatt.
A cardiac pacemaker or pacemakers are adapted for implantation in
the human body. In a specific embodiment, one or more leadless
cardiac pacemakers can be co-implanted with an implantable
cardioverter-defibrillator (ICD). Each leadless cardiac pacemaker
uses two or more electrodes located within, on, or within two
centimeters of the housing of the pacemaker, for pacing and sensing
at the cardiac chamber, for bidirectional communication with the
ICD, optionally with at least one other leadless cardiac pacemaker,
and optionally with at least one other device outside the body.
Referring to FIG. 1A, a pictorial diagram shows an embodiment of a
cardiac pacing system 100 including one or more leadless cardiac
pacemakers 102 with conducted communication for performing cardiac
pacing in conjunction with an implantable
cardioverter-defibrillator (ICD) 106. The system 100 can implement
for example single-chamber pacing, dual-chamber pacing, or
three-chamber pacing for cardiac resynchronization therapy, without
requiring pacing lead connections to the defibrillator 106. The
illustrative cardiac pacing system 100 comprises at least one
leadless cardiac pacemaker 102 configured for implantation in
electrical contact with a cardiac chamber 104 and configured to
perform cardiac pacing functions in combination with a co-implanted
implantable cardioverter-defibrillator (ICD) 106. One or more of
the leadless cardiac pacemakers 102 can comprise at least two
leadless electrodes 108 configured for delivering cardiac pacing
pulses, sensing evoked and/or natural cardiac electrical signals,
and uni-directionally or bi-directionally communicating with the
co-implanted ICD 106.
The leadless cardiac pacemakers 102 can communicate with one
another and/or communicate with a non-implanted programmer and/or
the implanted ICD 106 via the same electrodes 108 that are also
used to deliver pacing pulses. Usage of the electrodes 108 for
communication enables the one or more leadless cardiac pacemakers
102 for antenna-less and telemetry coil-less communication.
The leadless cardiac pacemakers 102 can be configured to
communicate with one another and to communicate with a
non-implanted programmer 106 via communication that has outgoing
communication power requirements essentially met by power consumed
in cardiac pacing.
In some embodiments, the individual leadless cardiac pacemaker 102
can comprise a hermetic housing 110 configured for placement on or
attachment to the inside or outside of a cardiac chamber 104 and at
least two leadless electrodes 108 proximal to the housing 110 and
configured for bidirectional communication with at least one other
device 106 within or outside the body. For example, FIG. 1B depicts
a single leadless cardiac pacemaker 102 and shows the pacemaker's
functional elements substantially enclosed in a hermetic housing
110. The pacemaker 102 has at least two electrodes 108 located
within, on, or near the housing 110, for delivering pacing pulses
to and sensing electrical activity from the muscle of the cardiac
chamber, and for bidirectional communication with at least one
other device within or outside the body. Hermetic feedthroughs 130,
131 conduct electrode signals through the housing 110. The housing
110 contains a primary battery 114 to supply power for pacing,
sensing, and communication. The housing 110 also contains circuits
132 for sensing cardiac activity from the electrodes 108, circuits
134 for receiving information from at least one other device via
the electrodes 108, and a pulse generator 116 for generating pacing
pulses for delivery via the electrodes 108 and also for
transmitting information to at least one other device via the
electrodes 108. The housing 110 can further contain circuits for
monitoring device health, for example a battery current monitor 136
and a battery voltage monitor 138, and can contain circuits 112 for
controlling operations in a predetermined manner.
The one or more leadless electrodes 108 can be configured to
communicate bidirectionally among the multiple leadless cardiac
pacemakers and/or the implanted ICD to coordinate pacing pulse
delivery using messages that identify an event at an individual
pacemaker originating the message and a pacemaker receiving the
message react as directed by the message depending on the origin of
the message. A pacemaker or pacemakers that receive the message
react as directed by the message depending on the message origin or
location. In some embodiments or conditions, the two or more
leadless electrodes 108 can be configured to communicate
bidirectionally among the one or more leadless cardiac pacemakers
102 and/or the ICD 106 and transmit data including designated codes
for events detected or created by an individual pacemaker.
Individual pacemakers can be configured to issue a unique code
corresponding to an event type and a location of the sending
pacemaker.
Information communicated on the incoming communication channel can
include but is not limited to pacing rate, pulse duration, sensing
threshold, and other parameters commonly programmed externally in
conventional pacemakers. Information communicated on the outgoing
communication channel can include but is not limited to
programmable parameter settings, pacing and sensing event counts,
battery voltage, battery current, device health, and other
information commonly displayed by external programmers used with
conventional pacemakers. The outgoing communication channel can
also echo information from the incoming channel, to confirm correct
programming.
In some embodiments, information encoded on the leadless cardiac
pacemakers can be used to enhance the sensitivity and specificity
of the ICD such as, for example, a subcutaneous-only implantable
defibrillator. Illustratively, a subcutaneously-only defibrillator
senses only far-field signals, making difficult extraction of
atrial information as well as uniquely identifying atrial
depolarization from ventricular depolarization. When a
subcutaneous-only defibrillator is used in combination with one or
more leadless cardiac pacemakers, the information derived from the
pacing pulse for each leadless pacemaker can be gathered and used
to identify atrial and ventricular depolarization without
ambiguity.
The leadless cardiac pacemaker 102 can communicate the information
listed hereinabove with the implanted ICD 106, or with a programmer
outside the body, or both.
For example, in some embodiments an individual pacemaker 102 of the
one or more leadless cardiac pacemakers can be configured to
deliver a coded pacing pulse with a code assigned according to
pacemaker location and configured to transmit a message to one or
more other leadless cardiac pacemakers via the coded pacing pulse
wherein the code identifies the individual pacemaker originating an
event. The pacemaker or pacemakers receiving the message are
adapted to respond to the message in a predetermined manner
depending on type and location of the event.
In some embodiments or conditions, individual pacemakers 102 can
deliver a coded pacing pulse with a code assigned according to
pacemaker location and configured to transmit a message to at least
one of the leadless cardiac pacemakers via the coded pacing pulse
wherein the code identifies the individual pacemaker originating an
event. The individual pacemakers can be further configured to
deliver a pacing pulse in absence of encoding whereby, for
dual-chamber cardiac pacing, a pacing pulse that is not generated
in a first cardiac pacemaker that senses the pacing pulse is
necessarily generated in a second cardiac pacemaker. Accordingly,
neither the use of a code to identify the chamber corresponding to
a pacing pulse, nor the use of a code to identify the type of pulse
(whether paced or sensed) is a necessary step in a simple system
such as a dual chamber pacing system disclosed in the
specification.
Moreover, information communicated on the incoming channel can also
include a message from another leadless cardiac pacemaker
signifying that the other leadless cardiac pacemaker has sensed a
heartbeat or has delivered a pacing pulse, and identifies the
location of the other pacemaker. Similarly, information
communicated on the outgoing channel can also include a message to
another leadless cardiac pacemaker or pacemakers, or to the ICD,
that the sending leadless cardiac pacemaker has sensed a heartbeat
or has delivered a pacing pulse at the location of the sending
pacemaker.
In some embodiments and in predetermined conditions, an individual
pacemaker 102 of the one or more leadless cardiac pacemakers can be
configured to communicate to one or more other implanted pacemakers
indication of the occurrence of a sensed heartbeat at the
individual pacemaker location via generation of a coded pacing
pulse triggered by the sensed heartbeat in a natural refractory
period following the sensed heartbeat.
Referring again to FIGS. 1A and 1B, in various embodiments a
cardiac pacing system 100 comprises at least one leadless cardiac
pacemaker 102 that is configured for implantation in electrical
contact with a cardiac chamber 104 and configured to perform
cardiac pacing functions in combination with a co-implanted
implantable cardioverter-defibrillator (ICD) 106.
An embodiment of a cardiac pacing system 100 comprises an
implantable cardioverter-defibrillator (ICD) 106 and at least one
leadless cardiac pacemaker 102 configured for implantation in
electrical contact with a cardiac chamber and for performing
cardiac rhythm management functions in combination with the
implantable ICD 106. The implantable ICD 106 and the one or more
leadless cardiac pacemakers 102 configured for leadless
intercommunication by information conduction through body
tissue.
In another embodiment, a cardiac pacing system 100 comprises one or
more leadless cardiac pacemaker 102 or pacemakers configured for
implantation in electrical contact with a cardiac chamber 104 and
configured to perform cardiac pacing functions in combination with
a co-implanted implantable cardioverter-defibrillator (ICD) 106.
The leadless cardiac pacemaker or pacemakers 102 are configured to
intercommunicate and/or to communicate with a non-implanted
programmer and/or the implanted ICD 106 via two or more electrodes
108 that are used for delivering pacing pulses. The pacemakers 102
are configured for antenna-less and telemetry coil-less
communication.
In a further embodiment, a cardiac pacing system 100 comprises at
least one leadless cardiac pacemaker 102 configured for
implantation in electrical contact with a cardiac chamber 104 and
configured to perform cardiac pacing functions in combination with
a co-implanted implantable cardioverter-defibrillator (ICD) 106.
The leadless cardiac pacemaker or pacemakers 102 comprise at least
two leadless electrodes 108 configured for delivering cardiac
pacing pulses, sensing evoked and/or natural cardiac electrical
signals, and transmitting information to the co-implanted ICD
106.
In another example embodiment, a cardiac pacing system 100
comprises at least one leadless cardiac pacemaker 102 configured
for implantation in electrical contact with a cardiac chamber 104
and configured to perform cardiac pacing functions in combination
with a co-implanted implantable cardioverter-defibrillator (ICD)
106. The leadless cardiac pacemaker or pacemakers 102 comprising at
least two leadless electrodes 108 configured for delivering cardiac
pacing pulses, sensing evoked and/or natural cardiac electrical
signals, and receiving information from the co-implanted ICD
106.
As shown in the illustrative embodiments, a leadless cardiac
pacemaker 102 can comprise two or more leadless electrodes 108
configured for delivering cardiac pacing pulses, sensing evoked
and/or natural cardiac electrical signals, and bidirectionally
communicating with the co-implanted ICD 106. A leadless cardiac
pacemaker 102 can be configured to communicate with other
pacemakers and/or communicate with a non-implanted programmer via
communication that has communication power requirements essentially
met by power consumed in cardiac pacing. For example, the leadless
cardiac pacemaker 102 can be configured to communicate with other
pacemakers and with a non-implanted programmer via communication
that has negligible transmission power requirements in addition to
power consumed in cardiac pacing.
Individual pacemakers of the one or more leadless cardiac
pacemakers 102 can be configured for operation in a particular
location and a particular functionality at manufacture and/or at
programming by an external programmer. Bidirectional communication
among the multiple leadless cardiac pacemakers can be arranged to
communicate notification of a sensed heartbeat or delivered pacing
pulse event and encoding type and location of the event to another
implanted pacemaker or pacemakers. The pacemaker or pacemakers
receiving the communication decode the information and respond
depending on location of the receiving pacemaker and predetermined
system functionality.
In some embodiments, individual pacemakers 102 of the one or more
leadless cardiac pacemakers can be configured to receive conducted
communication from a co-implanted cardioverter-defibrillator (ICD)
106 that configures the pacemakers 102 to deliver overdrive
anti-tachycardia pacing in response to a detected
tachyarrhythmia.
Also shown in FIG. 1B, the primary battery 114 has positive
terminal 140 and negative terminal 142. A suitable primary battery
has an energy density of at least 3 Wh/cc, a power output of 70
microwatts, a volume less than 1 cubic centimeter, and a lifetime
greater than 5 years.
One suitable primary battery uses beta-voltaic technology, licensed
to BetaBatt Inc. of Houston, Tex., USA, and developed under a trade
name DEC.TM. Cell, in which a silicon wafer captures electrons
emitted by a radioactive gas such as tritium. The wafer is etched
in a three-dimensional surface to capture more electrons. The
battery is sealed in a hermetic package which entirely contains the
low-energy particles emitted by tritium, rendering the battery safe
for long-term human implant from a radiological-health standpoint.
Tritium has a half-life of 12.3 years so that the technology is
more than adequate to meet a design goal of a lifetime exceeding 5
years.
Current from the positive terminal 140 of primary battery 114 flows
through a shunt 144 to a regulator circuit 146 to create a positive
voltage supply 148 suitable for powering the remaining circuitry of
the pacemaker 102. The shunt 144 enables the battery current
monitor 136 to provide the processor 112 with an indication of
battery current drain and indirectly of device health.
The illustrative power supply can be a primary battery 114 such as
a beta-voltaic converter that obtains electrical energy from
radioactivity. In some embodiments, the power supply can be
selected as a primary battery 114 that has a volume less than
approximately 1 cubic centimeter.
The leadless cardiac pacemaker or pacemakers 102 can be configured
to detect a natural cardiac depolarization, time a selected delay
interval, and deliver an information-encoded pulse during a
refractory period following the natural cardiac depolarization. By
encoding information in a pacing pulse, power consumed for
transmitting information is not significantly greater than the
power used for pacing. Information can be transmitted through the
communication channel with no separate antenna or telemetry coil.
Communication bandwidth is low with only a small number of bits
encoded on each pulse.
In some embodiments, information can be encoded using a technique
of gating the pacing pulse for very short periods of time at
specific points in the pacing pulse. During the gated sections of
the pulse, no current flows through the electrodes of a leadless
cardiac pacemaker. Timing of the gated sections can be used to
encode information. The specific length of a gated segment depends
on the programmer's ability to detect the gated section. A certain
amount of smoothing or low-pass filtering of the signal can be
expected from capacitance inherent in the electrode/skin interface
of the programmer as well as the electrode/tissue interface of the
leadless cardiac pacemaker. A gated segment is set sufficiently
long in duration to enable accurate detection by the programmer,
limiting the amount of information that can be transmitted during a
single pacing pulse. Accordingly, a technique for communication can
comprise generating stimulation pulses on stimulating electrodes of
an implanted biostimulator and encoding information onto generated
stimulation pulses. Encoding information onto the pulses can
comprise gating the stimulation pulses for selected durations at
selected timed sections in the stimulation pulses whereby gating
removes current flow through the stimulating electrodes and timing
of the gated sections encodes the information.
Another method of encoding information on pacing pulses involves
varying the timing between consecutive pacing pulses in a pulse
sequence. Pacing pulses, unless inhibited or triggered, occur at
predetermined intervals. The interval between any two pulses can be
varied slightly to impart information on the pulse series. The
amount of information, in bits, is determined by the time
resolution of the pulse shift. The steps of pulse shifting are
generally on the order of microseconds. Shifting pulses by up to
several milliseconds does not have an effect on the pacing therapy
and cannot be sensed by the patient, yet significant information
can be transmitted by varying pulse intervals within the
microsecond range. The method of encoding information in variation
of pulses is less effective if many of the pulses are inhibited or
triggered. Accordingly, a technique for communication can comprise
generating stimulation pulses on stimulating electrodes of an
implanted biostimulator and encoding information onto generated
stimulation pulses comprising selectively varying timing between
consecutive stimulation pulses.
Alternatively or in addition to encoding information in gated
sections and/or pulse interval, overall pacing pulse width can be
used to encode information.
The three described methods of encoding information on pacing
pulses can use the programmer to distinguish pacing pulses from the
patient's normal electrocardiogram, for example by recognition of
the specific morphology of the pacing pulse compared to the R-wave
generated during the cardiac cycle. For example, the external
programmer can be adapted to distinguish a generated cardiac pacing
pulse from a natural cardiac depolarization in an electrocardiogram
by performing comparative pattern recognition of a pacing pulse and
an R-wave produced during a cardiac cycle.
In an illustrative embodiment, the primary battery 114 can be
selected to source no more than 70 microwatts instantaneously since
a higher consumption may cause the voltage across the battery
terminals to collapse. Accordingly in one illustrative embodiment
the circuits depicted in FIG. 1B can be designed to consume no more
than a total of 64 microwatts. The design avoids usage of a large
filtering capacitor for the power supply or other accumulators such
as a supercapacitor or rechargeable secondary cell to supply peak
power exceeding the maximum instantaneous power capability of the
battery, components that would add volume and cost.
In various embodiments, the system can manage power consumption to
draw limited power from the battery, thereby reducing device
volume. Each circuit in the system can be designed to avoid large
peak currents. For example, cardiac pacing can be achieved by
discharging a tank capacitor (not shown) across the pacing
electrodes. Recharging of the tank capacitor is typically
controlled by a charge pump circuit. In a particular embodiment,
the charge pump circuit is throttled to recharge the tank capacitor
at constant power from the battery.
Implantable systems that communicate via long distance
radio-frequency (RF) schemes, for example Medical Implant
Communication Service (MICS) transceivers, which exhibit a peak
power requirement on the order of 10 milliwatts, and other RF or
inductive telemetry schemes are unable to operate without use of an
additional accumulator. Moreover, even with the added accumulator,
sustained operation would ultimately cause the voltage across the
battery to collapse.
In some embodiments, the controller 112 in one leadless cardiac
pacemaker 102 can access signals on the electrodes 108 and can
examine output pulse duration from another pacemaker for usage as a
signature for determining triggering information validity and, for
a signature arriving within predetermined limits, activating
delivery of a pacing pulse following a predetermined delay of zero
or more milliseconds. The predetermined delay can be preset at
manufacture, programmed via an external programmer, or determined
by adaptive monitoring to facilitate recognition of the triggering
signal and discriminating the triggering signal from noise. In some
embodiments or in some conditions, the controller 112 can examine
output pulse waveform from another leadless cardiac pacemaker for
usage as a signature for determining triggering information
validity and, for a signature arriving within predetermined limits,
activating delivery of a pacing pulse following a predetermined
delay of zero or more milliseconds.
Also shown in FIG. 2, a cylindrical hermetic housing 110 is shown
with annular electrodes 108 at housing extremities. In the
illustrative embodiment, the housing 110 can be composed of alumina
ceramic which provides insulation between the electrodes. The
electrodes 108 are deposited on the ceramic, and are platinum or
platinum-iridium.
Several techniques and structures can be used for attaching the
housing 110 to the interior or exterior wall of cardiac chamber
muscle 104.
A helix 226 and slot 228 enable insertion of the device
endocardially or epicardially through a guiding catheter. A
screwdriver stylet can be used to rotate the housing 110 and force
the helix 226 into muscle 104, thus affixing the electrode 108A in
contact with stimulable tissue. Electrode 108B serves as an
indifferent electrode for sensing and pacing. The helix 226 may be
coated for electrical insulation, and a steroid-eluting matrix may
be included near the helix to minimize fibrotic reaction, as is
known in conventional pacing electrode-leads.
In other configurations, suture holes 224 and 225 can be used to
affix the device directly to cardiac muscle with ligatures, during
procedures where the exterior surface of the heart is exposed.
Other attachment structures used with conventional cardiac
electrode-leads including tines or barbs for grasping trabeculae in
the interior of the ventricle, atrium, or coronary sinus may also
be used in conjunction with or instead of the illustrative
attachment structures.
Referring to FIG. 3, a pictorial view shows another embodiment of a
single leadless cardiac pacemaker 102 that can be used in a cardiac
pacing system 100 with at least one other pacemaker. The leadless
cardiac pacemaker 102 includes a cylindrical metal housing 310 with
an annular electrode 108A and a second electrode 108B. Housing 310
can be constructed from titanium or stainless steel. Electrode 108A
can be constructed using a platinum or platinum-iridium wire and a
ceramic or glass feed-thru to provide electrical isolation from the
metal housing. The housing can be coated with a biocompatible
polymer such as medical grade silicone or polyurethane except for
the region outlined by electrode 108B. The distance between
electrodes 108A and 108B should be approximately 1 cm to optimize
sensing amplitudes and pacing thresholds. A helix 226 and slot 228
can be used for insertion of the device endocardially or
epicardially through a guiding catheter. In addition, suture
sleeves 302 and 303 made from silicone can be used to affix to the
device directly to cardiac muscle with ligatures, for example in an
epicardial or other application.
Referring to FIG. 4, a typical output-pulse waveform for a
conventional pacemaker is shown. The approximately-exponential
decay is due to discharge of a capacitor in the pacemaker through
the approximately-resistive load presented by the electrodes and
leads. Typically the generator output is capacitor-coupled to one
electrode to ensure net charge balance. The pulse duration is shown
as T0 and is typically 500 microseconds.
When the depicted leadless pacemaker 102 is used in combination
with at least one other pacemaker or other pulse generator in the
cardiac pacing system 100 and is generating a pacing pulse but is
not optionally sending data for communication, the pacing waveform
of the leadless pacemaker 102 can also resemble the conventional
pacing pulse shown in FIG. 4.
Referring to FIG. 5, a time waveform graph depicts an embodiment of
an output-pacing pulse waveform adapted for communication. The
output-pulse waveform of the illustrative leadless pacemaker 102 is
shown during a time when the pacemaker 102 is optionally sending
data for communication and also delivering a pacing pulse, using
the same pulse generator 116 and electrodes 108 for both
functions.
FIG. 5 shows that the pulse generator 102 has divided the output
pulse into shorter pulses 501, 502, 503, 504; separated by notches
505, 506, and 507. The pulse generator 102 times the notches 505,
506, and 507 to fall in timing windows W1, W2, and W4 designated
508, 509, and 511 respectively. Note that the pacemaker 102 does
not form a notch in timing window W3 designated 510. The timing
windows are each shown separated by a time T1, approximately 100
microseconds in the example.
As controlled by processor 112, pulse generator 116 selectively
generates or does not generate a notch in each timing window 508,
509, 510, and 511 so that the device 102 encodes four bits of
information in the pacing pulse. A similar scheme with more timing
windows can send more or fewer bits per pacing pulse. The width of
the notches is small, for example approximately 15 microseconds, so
that the delivered charge and overall pulse width, specifically the
sum of the widths of the shorter pulses, in the pacing pulse is
substantially unchanged from that shown in FIG. 4. Accordingly, the
pulse shown in FIG. 5 can have approximately the same pacing
effectiveness as that shown in FIG. 4, according to the law of
Lapique which is well known in the art of electrical
stimulation.
In a leadless cardiac pacemaker, a technique can be used to
conserve power when detecting information carried on pacing pulses
from other implanted devices. The leadless cardiac pacemaker can
have a receiving amplifier that implements multiple gain settings
and uses a low-gain setting for normal operation. The low-gain
setting could be insufficiently sensitive to decode gated
information on a pacing pulse accurately but could detect whether
the pacing pulse is present. If an edge of a pacing pulse is
detected during low-gain operation, the amplifier can be switched
quickly to the high-gain setting, enabling the detailed encoded
data to be detected and decoded accurately. Once the pacing pulse
has ended, the receiving amplifier can be set back to the low-gain
setting. For usage in the decoding operation, the receiving
amplifier is configured to shift to the more accurate high-gain
setting quickly when activated. Encoded data can be placed at the
end of the pacing pulse to allow a maximum amount of time to invoke
the high-gain setting.
As an alternative or in addition to using notches in the
stimulation pulse, the pulses can be generated with varying
off-times, specifically times between pulses during which no
stimulation occurs. The variation of off-times can be small, for
example less than 10 milliseconds total, and can impart information
based on the difference between a specific pulse's off-time and a
preprogrammed off-time based on desired heart rate. For example,
the device can impart four bits of information with each pulse by
defining 16 off-times centered around the preprogrammed off-time.
FIG. 6 is a graph showing a sample pulse generator output which
incorporates a varying off-time scheme. In the figure, time T.sub.P
represents the preprogrammed pulse timing. Time T.sub.d is the
delta time associated with a single bit resolution for the data
sent by the pulse generator. The number of T.sub.d time increments
before or after the moment specified by T.sub.P gives the specific
data element transmitted. The receiver of the pulse generator's
communication has advance information of the time T.sub.P. The
communication scheme is primarily applicable to overdrive pacing in
which time T.sub.P is not dynamically changing or altered based on
detected beats.
FIG. 5 depicts a technique in which information is encoded in
notches in the pacing pulse. FIG. 6 shows a technique of conveying
information by modulating the off-time between pacing pulses.
Alternatively or in addition to the two illustrative coding
schemes, overall pacing pulse width can be used to impart
information. For example, a paced atrial beat may exhibit a pulse
width of 500 microseconds and an intrinsic atrial contraction can
be identified by reducing the pulse width by 30 microseconds.
Information can be encoded by the absolute pacing pulse width or
relative shift in pulse width. Variations in pacing pulse width can
be relatively small and have no impact on pacing effectiveness.
In some embodiments, a pacemaker 102 can use the leadless
electrodes 108 to communicate bidirectionally among multiple
leadless cardiac pacemakers and transmit data including designated
codes for events detected or created by an individual pacemaker
wherein the codes encode information using pacing pulse width.
To ensure the leadless cardiac pacemaker functions correctly, a
specific minimum internal supply voltage is maintained. When pacing
tank capacitor charging occurs, the supply voltage can drop from a
pre-charging level which can become more significant when the
battery nears an end-of-life condition and has reduced current
sourcing capability. Therefore, a leadless cardiac pacemaker can be
constructed with a capability to stop charging the pacing tank
capacitor when the supply voltage drops below a specified level.
When charging ceases, the supply voltage returns to the value prior
to the beginning of tank capacitor charging.
In another technique, the charge current can be lowered to prevent
the supply voltage from dropping below the specified level.
However, lowering the charge current can create difficulty in
ensuring pacing rate or pacing pulse amplitude are maintained,
since the lower charge current can extend the time for the pacing
tank capacitor to reach a target voltage level.
The illustrative scheme for transmitting data does not
significantly increase the current consumption of the pacemaker.
For example, the pacemaker could transmit data continuously in a
loop, with no consumption penalty.
The illustrative schemes for transmitting data enable assignment of
designated codes to events detected or caused by a leadless cardiac
pacemaker, such as sensing a heartbeat or delivering a pacing pulse
at the location of the pacemaker that senses the event. Individual
leadless cardiac pacemakers 102 in a system 100 can be configured,
either at manufacture or with instructions from an external
programmer or from the co-implanted ICD 106 as described
hereinabove, to issue a unique code corresponding to the type of
event and location of the leadless cardiac pacemaker. By delivery
of a coded pacing pulse with a code assigned according to the
pacemaker location, a leadless cardiac pacemaker can transmit a
message to any and all other leadless cardiac pacemakers 102 and
the ICD 106 implanted in the same patient, where the code signifies
the origin of the event. Each other leadless cardiac pacemaker can
react appropriately to the conveyed information in a predetermined
manner encoded in the internal processor 112, as a function of the
type and location of the event coded in the received pulse. The ICD
106 can also use the information for arrhythmia detection. A
leadless cardiac pacemaker 102 can thus communicate to any and all
other co-implanted leadless cardiac pacemakers and to the
co-implanted ICD 106 the occurrence of a sensed heartbeat at the
originating pacemaker's location by generating a coded pacing pulse
triggered by the sensed event. Triggered pacing occurs in the
natural refractory period following the heartbeat and therefore has
no effect on the chamber where the leadless cardiac pacemaker is
located.
Referring again to FIG. 1B, the circuit 132 for receiving
communication via electrodes 108 receives the triggering
information as described and can also optionally receive other
communication information, either from the other implanted pulse
generator 106 or from a programmer outside the body. This other
communication could be coded with a pulse-position scheme as
described in FIG. 5 or could otherwise be a pulse-modulated or
frequency-modulated carrier signal, preferably from 10 kHz to 100
kHz. The illustrative scheme of a modulated carrier is applicable
not only to intercommunication among multiple implanted pacemakers
but also is applicable to communication from an external programmer
or the co-implanted ICD 106.
The illustrative leadless pacemaker 102 could otherwise receive
triggering information from the other pulse generator 106 implanted
within the body via a pulse-modulated or frequency-modulated
carrier signal, instead of via the pacing pulses of the other pulse
generator 106.
With regard to operating power requirements in the leadless cardiac
pacemaker 102, for purposes of analysis, a pacing pulse of 5 volts
and 5 milliamps amplitude with duration of 500 microseconds and a
period of 500 milliseconds has a power requirement of 25
microwatts.
In an example embodiment of the leadless pacemaker 102, the
processor 112 typically includes a timer with a slow clock that
times a period of approximately 10 milliseconds and an
instruction-execution clock that times a period of approximately 1
microsecond. The processor 112 typically operates the
instruction-execution clock only briefly in response to events
originating with the timer, communication amplifier 134, or cardiac
sensing amplifier 132. At other times, only the slow clock and
timer operate so that the power requirement of the processor 112 is
no more than 5 microwatts.
For a pacemaker that operates with the aforementioned slow clock,
the instantaneous power consumption specification, even for a
commercially-available micropower microprocessor, would exceed the
battery's power capabilities and would require an additional filter
capacitor across the battery to prevent a drop of battery voltage
below the voltage necessary to operate the circuit. The filter
capacitor would add avoidable cost, volume, and potentially lower
reliability.
For example, a microprocessor consuming only 100 microamps would
require a filter capacitor of 5 microfarads to maintain a voltage
drop of less than 0.1 volt, even if the processor operates for only
5 milliseconds. To avoid the necessity for such a filter capacitor,
an illustrative embodiment of a processor can operate from a lower
frequency clock to avoid the high instantaneous power consumption,
or the processor can be implemented using dedicated hardware state
machines to supply a lower instantaneous peak power
specification.
In a pacemaker, the cardiac sensing amplifier typically operates
with no more than 5 microwatts. A communication amplifier at 100
kHz operates with no more than 25 microwatts. The battery ammeter
and battery voltmeter operate with no more than 1 microwatt
each.
A pulse generator typically includes an independent rate limiter
with a power consumption of no more than 2 microwatts.
The total power consumption of the pacemaker is thus 64 microwatts,
less than the disclosed 70-microwatt battery output.
Improvement attained by the illustrative cardiac pacing system 100
and leadless cardiac pacemaker 102 is apparent.
In a specific embodiment, the outgoing communication power
requirement plus the pacing power requirement does not exceed
approximately 25 microwatts. In other words, outgoing communication
adds essentially no power to the power used for pacing.
The illustrative leadless cardiac pacemaker 102 can have sensing
and processing circuitry that consumes no more than 10 microwatts
as in conventional pacemakers.
The described leadless cardiac pacemaker 102 can have an incoming
communication amplifier for receiving triggering signals and
optionally other communication which consumes no more than 25
microwatts.
Furthermore, the leadless cardiac pacemaker 102 can have a primary
battery that exhibits an energy density of at least 3 watt-hours
per cubic centimeter (Wh/cc).
In an illustrative application of the cardiac pacing system 100,
one or more leadless cardiac pacemakers 102 can be co-implanted
with an ICD 106 in a single patient to provide a system for
single-chamber pacing, dual-chamber pacing, CRT-D, or any other
multi-chamber pacing application. Each leadless cardiac pacemaker
in the system can use the illustrative communication structures to
communicate the occurrence of a sensed heartbeat or a delivered
pacing pulse at the location of sensing or delivery, and a
communication code can be assigned to each combination of event
type and location. Each leadless cardiac pacemaker can receive the
transmitted information, and the code of the information can
signify that a paced or sensed event has occurred at another
location and indicate the location of occurrence. The receiving
leadless cardiac pacemaker's processor 112 can decode the
information and respond appropriately, depending on the location of
the receiving pacemaker and the desired function of the system.
The implanted cardioverter-defibrillator (ICD) 106 can comprise a
case and be fitted with a pair of electrodes mounted on or near the
case. The ICD 106 can be configured to receive and transmit
conducted communication using a pulse modulated or frequency
modulated carrier signal whereby the ICD 106 can detect
communication pulses from co-implanted leadless cardiac pacemakers
102 and transmit programming information to the co-implanted
leadless cardiac pacemakers 102. In some embodiments, an implanted
cardioverter-defibrillator (ICD) 106 configured to receive
conducted communication using two implantable electrodes.
FIGS. 7 and 8 are state diagrams that illustrate application of
illustrative combined control operations in an atrial and
right-ventricular leadless cardiac pacemaker respectively, to
implement a simple dual-chamber pacing system when co-implanted
with an ICD 106. FIG. 9 is a state diagram that illustrates
inclusion of a left-ventricular leadless cardiac pacemaker to form
a CRT-D system. In various embodiments, each leadless cardiac
pacemaker may also broadcast other information destined for
co-implanted leadless cardiac pacemakers and the co-implanted ICD,
besides markers of paced or sensed events.
For clarity of illustration, descriptions of the atrial, right
ventricular, and left-ventricular leadless cardiac pacemakers in
respective FIGS. 7, 8, and 9 show only basic functions of each
pacemaker. Other functions such as refractory periods, fallback
mode switching, algorithms to prevent pacemaker-mediated
tachycardia, and the like, can be added to the leadless cardiac
pacemakers and to the system in combination. Also for clarity,
functions for communication with an external programmer are not
shown and are shown elsewhere herein.
Referring to FIG. 7, a state-mechanical representation shows
operation of a leadless cardiac pacemaker for implantation adjacent
to atrial cardiac muscle. As explained above, a leadless cardiac
pacemaker can be configured for operation in a particular location
and system either at manufacture or by an external programmer.
Similarly, all individual pacemakers of the multiple pacemaker
system can be configured for operation in a particular location and
a particular functionality at manufacture and/or at programming by
an external programmer wherein "configuring" means defining logic
such as a state machine and pulse codes used by the leadless
cardiac pacemaker.
In a cardiac pacing system, the multiple leadless cardiac
pacemakers can comprise an atrial leadless cardiac pacemaker
implanted in electrical contact to an atrial cardiac chamber. The
atrial leadless cardiac pacemaker can be configured or programmed
to perform several control operations 700 in combination with one
or more other pacemakers. In a wait state 702 the atrial leadless
cardiac pacemaker waits for an earliest occurring event of multiple
events including a sensed atrial heartbeat 704, a communication of
an event sensed on the at least two leadless electrodes encoding a
pacing pulse marking a heartbeat 706 at a ventricular leadless
cardiac pacemaker, or timeout of an interval timed locally in the
atrial leadless cardiac pacemaker shown as escape interval timeout
708. The atrial pacemaker responds to a sensed atrial heartbeat 704
by generating 710 an atrial pacing pulse that signals to one or
more other pacemakers and optionally to the co-implanted ICD that
an atrial heartbeat has occurred, encoding the atrial pacing pulse
with a code signifying an atrial location and a sensed event type.
The atrial pacing pulse can be encoded using the technique shown in
FIG. 5 with a unique code signifying the location in the atrium.
After pacing the atrium, the atrial cardiac pacemaker times 712 a
predetermined atrial-to-atrial (AA) escape interval. Accordingly,
the atrial leadless cardiac pacemaker restarts timing 712 for a
predetermined escape interval, called the AA (atrial to atrial)
escape interval, which is the time until the next atrial pacing
pulse if no other event intervenes. The atrial leadless cardiac
pacemaker then re-enters the Wait state 702. The atrial pacemaker
also responds to timeout of a first occurring escape interval 708
by delivering an atrial pacing pulse 710, causing an atrial
heartbeat with the atrial pacing pulse encoding paced type and
atrial location of an atrial heartbeat event. When the atrial
escape interval times out, shown as transition 708, the atrial
leadless cardiac pacemaker delivers an atrial pacing pulse. Because
no other atrial heartbeat has occurred during the duration of the
escape interval, the atrial pacing pulse does not fall in the
atria's natural refractory period and therefore should effectively
pace the atrium, causing an atrial heartbeat. The atrial pacing
pulse, coded in the manner shown in FIG. 5, also signals to any and
all other co-implanted leadless cardiac pacemakers and optionally
to the co-implanted ICD that an atrial heartbeat has occurred. If
functionality is enhanced for a more complex system, the atrial
leadless cardiac pacemaker can use a different code to signify
synchronous pacing triggered by an atrial sensed event in
comparison to the code used to signify atrial pacing at the end of
an escape interval. However, in the simple example shown in FIGS. 7
and 8, the same code can be used for all atrial pacing pulses. In
fact, for the simple dual-chamber pacing system described in FIGS.
7 and 8 encoding may be omitted because each leadless cardiac
pacemaker can conclude that any detected pacing pulse, which is not
generated locally, must have originated with the other co-implanted
leadless cardiac pacemaker. After generating the atrial pacing
pulse 710, the atrial leadless cardiac pacemaker starts timing an
atrial (AA) escape interval at action 712, and then returns to the
wait state 702.
The atrial leadless cardiac pacemaker can further operate in
response to another pacemaker. The atrial pacemaker can detect 706
a signal originating from a co-implanted ventricular leadless
cardiac pacemaker. The atrial pacemaker can examine the elapsed
amount of the atrial-to-atrial (AA) escape time interval since a
most recent atrial heartbeat and determine 714 whether the signal
originating from the co-implanted ventricular leadless cardiac
pacemaker is premature. Thus, if the atrial leadless cardiac
pacemaker detects a signal originating from a co-implanted
ventricular leadless cardiac pacemaker, shown as sensed ventricular
pacing 706, then the atrial device examines the amount of the
escape interval elapsed since the last atrial heartbeat at decision
point 714 to determine whether the ventricular event is
"premature", meaning too late to be physiologically associated with
the last atrial heartbeat and in effect premature with respect to
the next atrial heartbeat. In the absence 716 of a premature
signal, the atrial pacemaker waits 702 for an event with no effect
on atrial pacing. In contrast if the signal is premature 718, the
pacemaker restarts 720 a ventricle-to-atrium (VA) escape interval
that is shorter than the atrial-to-atrial (AA) escape interval and
is representative of a typical time from a ventricular beat to a
next atrial beat in sinus rhythm, specifically the atrial interval
minus the atrio-ventricular conduction time. After starting 720 the
VA interval, the atrial leadless cardiac pacemaker returns to wait
state 702, whereby a ventricular premature beat can be said to
"recycle" the atrial pacemaker. The pacemaker responds to timeout
of the atrial-to-atrial (AA) escape interval 708 by delivering an
atrial pacing pulse 710, causing an atrial heartbeat. The atrial
pacing pulse encodes the paced type and atrial location of an
atrial heartbeat event.
The atrial leadless cardiac pacemaker can be further configured to
time a prolonged post-ventricular atrial refractory period (PVARP)
after recycling in presence of the premature signal, thereby
preventing pacemaker-mediated tachycardia (PMT). Otherwise, if a
received ventricular pacing signal evaluated at decision point 714
is not found to be premature, then the atrial leadless cardiac
pacemaker follows transition 716 and re-enters the wait state 702
without recycling, thus without any effect on the timing of the
next atrial pacing pulse.
Referring to FIG. 8, a state-mechanical representation depicts
operation of a leadless cardiac pacemaker for implantation adjacent
to right-ventricular cardiac muscle. The leadless cardiac pacemaker
can be configured for operation in a particular location and system
either at manufacture or by an external programmer. A system
comprising multiple leadless cardiac pacemakers can include a
right-ventricular leadless cardiac pacemaker implanted in
electrical contact to a right-ventricular cardiac chamber. The
right-ventricular leadless cardiac pacemaker can be configured to
perform actions 800 for coordinated pacing in combination with the
other pacemakers. The right-ventricular leadless cardiac pacemaker
waits 802 for the earliest occurring event of multiple events
including a sensed right-ventricular heartbeat 804, a sensed
communication of a pacing pulse 806 marking a heartbeat at an
atrial leadless cardiac pacemaker, and timeout 808 of an escape
interval. Generally, the sensed communication of a pacing pulse 806
can be any suitable sensed communication of an event originating at
another co-implanted leadless cardiac pacemaker, in the
illustrative embodiment a pacing pulse marking a heartbeat at an
atrial leadless cardiac pacemaker shown as sensed atrial pacing.
The escape interval timeout 808 can be any suitable timeout of an
interval timed locally in the right-ventricular leadless cardiac
pacemaker.
The right-ventricular leadless cardiac pacemaker responds to the
sensed right-ventricular heartbeat 804 by generating 810 a
right-ventricular pacing pulse that signals to at least one other
pacemaker of the multiple cardiac pacemakers and optionally to the
co-implanted ICD that a right-ventricular heartbeat has occurred.
Thus, when a sensed right-ventricular heartbeat occurs 804, the
right-ventricular leadless cardiac pacemaker generates 810 a
right-ventricular pacing pulse, not to pace the heart but rather to
signal to another leadless cardiac pacemaker or pacemakers that a
right-ventricular heartbeat has occurred. The right-ventricular
pacing pulse can be encoded with a code signifying the
right-ventricular location and a sensed event type. The
right-ventricular pacing pulse is coded in the manner shown in FIG.
5 with a unique code signifying the location in the right
ventricle. Upon right-ventricular pacing pulse generation 810, the
right-ventricular leadless cardiac pacemaker can time 812 a
predetermined right ventricular-to-right ventricular (VV) escape
interval. The right-ventricular leadless cardiac pacemaker restarts
812 timing of a predetermined escape interval, called the VV
(right) (right-ventricular to right-ventricular) escape interval,
which is the time until the next right-ventricular pacing pulse if
no other event intervenes.
The right-ventricular leadless cardiac pacemaker can further be
configured to set the ventricular-to-ventricular (VV) escape
interval longer than a predetermined atrial-to-atrial (AA) escape
interval to enable backup ventricular pacing at a low rate
corresponding to the VV escape interval in case of failure of a
triggered signal from a co-implanted atrial leadless cardiac
pacemaker. Typically, the VV (right) escape interval is longer than
the AA interval depicted in FIG. 7, so that the system supports
backup ventricular pacing at a relatively low rate in case of
failure of the co-implanted atrial leadless cardiac pacemaker. In
normal operation of the system, timeout of the VV interval never
occurs. The right-ventricular leadless cardiac pacemaker then
re-enters the Wait state 802.
The right-ventricular leadless cardiac pacemaker can respond to
timeout of a first occurring escape interval 808 by delivering 810
a right ventricular pacing pulse, causing a right ventricular
heartbeat. The right ventricular pacing pulse can encode
information including paced type and right-ventricular location of
a right ventricular heartbeat event.
When the right-ventricular escape interval times out 808, the
right-ventricular leadless cardiac pacemaker delivers 810 a
right-ventricular pacing pulse. Because no other right-ventricular
heartbeat has occurred during the duration of the VV escape
interval, the pacing pulse 810 does not fall in the ventricles'
natural refractory period and therefore should effectively pace the
ventricles, causing a ventricular heartbeat. The right-ventricular
pacing pulse, coded in the manner shown in FIG. 5, also signals to
any and all other co-implanted leadless cardiac pacemakers and
optionally to the co-implanted ICD that a right-ventricular
heartbeat has occurred. If useful for the function of a more
complex system, the right-ventricular leadless cardiac pacemaker
can use a different code to signify synchronous pacing triggered by
a right-ventricular sensed event in comparison to the code used to
signify right-ventricular pacing at the end of a VV escape
interval. However, in the simple example shown in FIGS. 7 and 8,
the same code can be used for all right-ventricular pacing pulses.
In fact, for the simple dual-chamber pacing system described in
FIGS. 7 and 8, a code may be omitted because each leadless cardiac
pacemaker can conclude that any detected pacing pulse which is not
generated local to the pacemaker originates with the other
co-implanted leadless cardiac pacemaker. After generating 810 the
right-ventricular pacing pulse, the right-ventricular leadless
cardiac pacemaker starts timing 812 a right-ventricular escape
interval VV, and then returns to the wait state 802.
The right-ventricular leadless cardiac pacemaker can further be
configured to detect 806 a signal originating from a co-implanted
atrial leadless cardiac pacemaker. The right-ventricular leadless
cardiac pacemaker examines the elapsed amount of the
ventricular-to-ventricular (VV) escape interval since a most recent
right-ventricular heartbeat and determines 814 whether the signal
originating from the co-implanted atrial leadless cardiac pacemaker
is premature. An atrial event is defined as premature if too early
to trigger an atrio-ventricular delay to produce a
right-ventricular heartbeat. In the presence of a premature signal
816, the right-ventricular leadless cardiac pacemaker returns to
the wait state 802 with no further action. Thus, a premature atrial
beat does not affect ventricular pacing. In the absence of a
premature signal 818, the right-ventricular leadless cardiac
pacemaker starts 820 a right atrium to right ventricular (AV)
escape interval that is representative of a typical time from an
atrial beat to a right-ventricular beat in sinus rhythm. Thus a
non-premature atrial event leads to starting 820 an AV (right)
atrium to right-ventricular escape interval that represents a
typical time from an atrial beat to a right-ventricular beat in
normally-conducted sinus rhythm. After starting 820 the AV
interval, the right-ventricular leadless cardiac pacemaker returns
to the wait state 802 so that a non-premature atrial beat can
"trigger" the right-ventricular pacemaker after a physiological
delay. The right-ventricular leadless cardiac pacemaker also
responds to timeout of either the VV escape interval and the AV
escape interval 808 by delivering 810 a right ventricular pacing
pulse, causing a right ventricular heartbeat. The right ventricular
pacing pulse encodes paced type and right-ventricular location of a
right ventricular heartbeat event.
Accordingly, co-implanted atrial and right-ventricular leadless
cardiac pacemakers depicted in FIGS. 7 and 8 cooperate to form a
dual-chamber pacing system.
Referring to FIG. 9, a state-mechanical representation illustrates
the operation of a leadless cardiac pacemaker for implantation
adjacent to left-ventricular cardiac muscle. The left-ventricular
cardiac pacemaker can be used in combination with the dual-chamber
pacemaker that includes the atrial leadless cardiac pacemaker and
the right-ventricular leadless cardiac pacemaker described in FIGS.
7 and 8 respectively to form a system for CRT-D. A leadless cardiac
pacemaker, for example the left-ventricular cardiac pacemaker, can
be configured for operation in a particular location and system
either at manufacture or by an external programmer.
A cardiac pacing system, such as a CRT-D system, can include
multiple leadless cardiac pacemakers including a left-ventricular
leadless cardiac pacemaker implanted in electrical contact to a
left-ventricular cardiac chamber. The left-ventricular leadless
cardiac pacemaker can execute operations of an illustrative pacing
method 900. In a wait state 902, the left-ventricular cardiac
pacemaker waits 902 at the left-ventricular leadless cardiac
pacemaker for an earliest occurring event of multiple events
including a sensed communication 904 of a pacing pulse marking a
heartbeat at an atrial leadless cardiac pacemaker and timeout 906
of a left ventricular escape interval. Generally, the sensed
communication 904 can be the sensed communication of an event
originating at another co-implanted leadless cardiac pacemaker, in
the illustrative embodiment a pacing pulse marking a heartbeat at
an atrial leadless cardiac pacemaker shown as sensed atrial pacing.
The escape interval timeout 906 can be timeout of an interval timed
locally in the left-ventricular leadless cardiac pacemaker. In the
wait state 902 for the left-ventricular leadless cardiac pacemaker,
operation is simplified and the left-ventricular pacemaker does not
respond to left-ventricular heartbeats. Also, the left-ventricular
cardiac pacemaker does not pace the left ventricle in the absence
of a triggering signal from the atrial leadless cardiac pacemaker.
The left-ventricular cardiac pacemaker responds to timeout 906 of
the left ventricular escape interval by delivering 908 a left
ventricular pacing pulse, causing a left ventricular heartbeat. The
left ventricular pacing pulse encodes the type and location of a
left ventricular heartbeat event. The left-ventricular pacing pulse
can be coded in the manner shown in FIG. 5 to communicate signals
to any and all other co-implanted leadless cardiac pacemakers and
optionally to the co-implanted ICD that a left-ventricular
heartbeat has occurred, although such encoding is not necessary in
the simplified CRT-D system shown in the described embodiment
because the other leadless cardiac pacemakers do not react to
left-ventricular pacing. After generating 908 the left-ventricular
pacing pulse, the left-ventricular leadless cardiac pacemaker
returns to the wait state 902.
The left-ventricular leadless cardiac pacemaker can be further
configured detect a signal originating from a co-implanted atrial
leadless cardiac pacemaker and examine the elapsed amount of the
left ventricular escape interval since a most recent
left-ventricular heartbeat. The left-ventricular cardiac pacemaker
can determine 910 whether the signal originating from the
co-implanted atrial leadless cardiac pacemaker is premature. If the
left-ventricular leadless cardiac pacemaker detects sensed atrial
pacing, then the left-ventricular device determines whether the
atrial event is premature, meaning too early to trigger an
atrio-ventricular delay to produce a left-ventricular heartbeat. In
the presence of a premature signal 912, the left-ventricular
cardiac pacemaker reverts to the wait state 902 and waits for an
event with no effect on ventricular pacing so that a premature
atrial beat does not affect ventricular pacing. In absence of a
premature signal 914, the left-ventricular cardiac pacemaker starts
916 a left atrium to left ventricular (AV) escape interval that is
representative of a typical time from an atrial beat to a left
ventricular beat in normally-conducted sinus rhythm. As shown in
the depicted embodiment, the AV (left) escape interval can have a
different value from the AV (right) escape interval. After starting
916 the AV interval, the left-ventricular leadless cardiac
pacemaker returns to wait state 902. Accordingly, a non-premature
atrial beat can "trigger" the left-ventricular pacemaker after a
physiological delay.
The left-ventricular cardiac pacemaker also responds to timeout 906
of the AV escape interval by delivering 908 a left ventricular
pacing pulse, causing a left ventricular heartbeat. The left
ventricular pacing pulse encodes paced type and left ventricular
location of a left ventricular heartbeat event.
In various embodiments, the multiple leadless cardiac pacemakers
can comprise a right ventricular leadless cardiac pacemaker and a
left ventricular leadless cardiac pacemaker that are configured to
operate with atrio-ventricular (AV) delays whereby a left
ventricular pacing pulse can be delivered before, after, or
substantially simultaneously with a right ventricular pacing pulse.
For example, multiple co-implanted leadless cardiac pacemakers that
function according to the state diagrams shown in FIGS. 7, 8, and 9
can support CRT-D with left-ventricular pacing delivered before, at
the same time as, or after right-ventricular pacing.
The co-implanted ICD can configure the leadless cardiac pacemakers
via conducted communication in a similar manner to an external
programmer. In particular, the ICD can configure them to deliver
overdrive anti-tachycardia pacing in response to detected
tachyarrhythmias.
In various embodiments, multiple co-implanted leadless cardiac
pacemakers can be configured for multi-site pacing that
synchronizes depolarization for tachyarrhythmia prevention.
The illustrative system can be useful in conjunction with an ICD,
and more particularly with a subcutaneous ICD, for such an ICD has
no other means to provide bradycardia support, anti-tachycardia
pacing, and CRT.
Referring to FIGS. 10A, 10B, 11A, 11B, 12A, and 12B, schematic flow
charts illustrate an embodiment of a method for operating a cardiac
pacing system that comprises an implantable
cardioverter-defibrillator (ICD) and one or more leadless cardiac
pacemakers configured for implantation in electrical contact with a
cardiac chamber and configured for performing cardiac pacing
functions in combination with the ICD. Pacing functions include
delivering cardiac pacing pulses, sensing evoked and/or natural
cardiac electrical signals, and bidirectionally communicating with
a co-implanted ICD and/or at least one other pacemaker. The one or
more leadless cardiac pacemakers are further configured to
communicate a code that signifies occurrence of sensed cardiac
electrical signals and/or delivered pacing pulses and identifies an
event type and/or location.
Two or more electrodes are coupled to the ICD and configured to
transmit and/or receive conducted communication using a
pulse-modulated or frequency-modulated carrier signal. The ICD can
be configured to detect communication pulses from at least one
co-implanted leadless cardiac pacemaker and transmit programming
information to the at least one co-implanted leadless cardiac
pacemaker.
The leadless cardiac pacemakers can be configured to broadcast
information to the co-implanted ICD and/or at least one other
pacemaker. The leadless cardiac pacemakers can further be
configured to receive the code and react based on the code,
location of the receiving leadless cardiac pacemaker, and
predetermined system functionality.
In various embodiments, configurations, and conditions, the
leadless cardiac pacemakers can be adapted to perform one or more
cardiac pacing functions such as single-chamber pacing,
dual-chamber pacing, cardiac resynchronization therapy with
cardioversion/defibrillation (CRT-D), single-chamber overdrive
pacing for prevention of tachyarrhythmias, single-chamber overdrive
pacing for conversion of tachyarrhythmias, multiple-chamber pacing
for prevention of tachyarrhythmias, multiple-chamber pacing for
conversion of tachyarrhythmias, and the like.
Multiple leadless cardiac pacemakers can be configured for
co-implantation in a single patient and multiple-chamber pacing
including CRT-D. Bidirectional communication among the multiple
leadless cardiac pacemakers can be adapted to communicate
notification of a sensed heartbeat or delivered pacing pulse event
and encoding type and location of the event to at least one
pacemaker of the leadless cardiac pacemaker plurality. The one or
more pacemakers that receive the communication can decode the
information and react depending on location of the receiving
pacemaker and predetermined system functionality.
FIG. 10A depicts a method 1000 for operating one or more leadless
cardiac pacemakers including an atrial leadless cardiac pacemaker
that is implanted in electrical contact to an atrial cardiac
chamber and configured for dual-chamber pacing in combination with
the co-implanted ICD. Cardiac pacing comprises configuring 1002 a
multiple leadless cardiac pacemakers for implantation and
configuring 1004 an atrial leadless cardiac pacemaker of the
multiple leadless cardiac pacemakers for implantation in electrical
contact to an atrial cardiac chamber. The atrial leadless cardiac
pacemaker waits 1006 for an earliest occurring event of multiple
events including a sensed atrial heartbeat, a communication of an
event sensed on the at least two leadless electrodes encoding a
pacing pulse marking a heartbeat at a ventricular leadless cardiac
pacemaker, and timeout of an atrial-to-atrial (AA) escape interval.
The atrial leadless cardiac pacemaker responds 1008 to the sensed
atrial heartbeat by generating an atrial pacing pulse that signals
to at least one pacemaker of the multiple leadless cardiac
pacemakers and optionally to the co-implanted ICD that an atrial
heartbeat has occurred and that encodes the atrial pacing pulse
with a code signifying an atrial location and a sensed event type.
After either a sensed atrial heartbeat or timeout of an escape
interval, the atrial leadless cardiac pacemaker delivers 1010 an
atrial pacing pulse, causing an atrial heartbeat and starts 1012
timing a predetermined length AA escape interval, then waiting 1006
for an event. The atrial pacing pulse identifies paced type and/or
atrial location of an atrial heartbeat event.
In some embodiments, the atrial leadless cardiac pacemaker can
encode an atrial pacing pulse that identifies synchronous pacing
triggered by an atrial sensed event with a first code and encode an
atrial pacing pulse that identifies atrial pacing following the AA
escape interval with a second code distinct from the first
code.
The atrial leadless cardiac pacemaker can, upon delivery of an
atrial pacing pulse, time an atrial-to-atrial (AA) escape
interval.
FIG. 10B is a flow chart showing another aspect 1050 of the method
embodiment for operating an atrial leadless cardiac pacemaker. The
atrial leadless cardiac pacemaker detects 1052 a signal originating
from a co-implanted ventricular leadless cardiac pacemaker and
examines 1054 an elapsed amount of the atrial-to-atrial (AA) escape
interval since a most recent atrial heartbeat, determining 1056
whether the signal originating from the co-implanted ventricular
leadless cardiac pacemaker is premature. In absence of a premature
signal 1058, the atrial leadless cardiac pacemaker waits 1060 for
an event with no effect on atrial pacing, returning to wait state
1006. In presence of a premature signal 1062, the atrial leadless
cardiac pacemaker restarts 1064 a ventricle-to-atrium (VA) escape
interval that is shorter than the atrial-to-atrial (AA) escape
interval and representative of a typical time from a ventricular
beat to a next atrial beat in sinus rhythm, then returns to wait
state 1006.
Referring to FIGS. 11A and 11B, schematic flow charts illustrate an
embodiment of a method for operating a right-ventricular leadless
cardiac pacemaker in an illustrative multi-chamber cardiac pacing
system. The right-ventricular leadless cardiac pacemaker is
implanted in electrical contact to a right-ventricular cardiac
chamber and configured for dual-chamber pacing in combination with
the co-implanted ICD. FIG. 11A depicts a method 1100 for cardiac
pacing comprising configuring 1102 a plurality of leadless cardiac
pacemakers for implantation and configuring 1104 a
right-ventricular leadless cardiac pacemaker of the multiple
leadless cardiac pacemakers for implantation in electrical contact
to a right-ventricular cardiac chamber. The right-ventricular
leadless cardiac pacemaker waits 1106 for an earliest occurring
event of a several events including a sensed right-ventricular
heartbeat, a sensed communication of a pacing pulse marking a
heartbeat at an atrial leadless cardiac pacemaker, and timeout of
an escape interval. The right-ventricular leadless cardiac
pacemaker responds 1108 to the sensed right-ventricular heartbeat
by generating a right-ventricular pacing pulse that signals to at
least one pacemaker of the leadless cardiac pacemakers and
optionally to the co-implanted ICD that a right-ventricular
heartbeat has occurred and that encodes the right-ventricular
pacing pulse with a code signifying a right-ventricular location
and a sensed event type. The right-ventricular leadless cardiac
pacemaker responds 1110 to timeout of a first-occurring escape
interval by delivering a right ventricular pacing pulse, causing a
right ventricular heartbeat, with the right ventricular pacing
pulse encoding paced type and right ventricular location of a right
ventricular heartbeat event, and times 1112 a predetermined
ventricular-to-ventricular (VV) escape interval.
In some embodiments, the right-ventricular leadless cardiac
pacemaker can encode a right-ventricular pacing pulse that
identifies synchronous pacing triggered by a right-ventricular
sensed event with a first code and encode a right-ventricular
pacing pulse that identifies right-ventricular pacing following a
ventricular-to-ventricular (VV) escape interval with a second code
distinct from the first code.
In some embodiments, the right-ventricular leadless cardiac
pacemaker, upon delivery of a right-ventricular pacing pulse, can
time a ventricular-to-ventricular (VV) escape interval.
FIG. 11B is a flow chart showing another aspect of an embodiment of
a method 1150 for operating a right-ventricular leadless cardiac
pacemaker. The right-ventricular leadless cardiac pacemaker detects
1152 a signal originating from a co-implanted atrial leadless
cardiac pacemaker, examines 1154 the elapsed amount of the
ventricular-to-ventricular (VV) escape interval since a most recent
right-ventricular heartbeat, and determines 1156 whether the signal
originating from the co-implanted atrial leadless cardiac pacemaker
is premature. In presence 1158 of a premature signal, the
right-ventricular leadless cardiac pacemaker waits 1160 for an
event with no effect on ventricular pacing, returning to wait state
1106. In absence 1162 of a premature signal, the right-ventricular
leadless cardiac pacemaker starts 1164 a right atrium to right
ventricular (AV) escape interval that is representative of a
typical time from an atrial beat to a right-ventricular beat in
sinus rhythm, and then returns to the wait state 1106.
Referring to FIGS. 12A and 12B, schematic flow charts illustrate
embodiments of a method for operating a left-ventricular leadless
cardiac pacemaker in multi-chamber cardiac pacing system. The
left-ventricular leadless cardiac pacemaker is implanted in
electrical contact to a left-ventricular cardiac chamber and
configured for dual-chamber pacing in combination with the
co-implanted ICD. FIG. 12A depicts a method 1200 for cardiac pacing
comprising configuring 1202 a plurality of leadless cardiac
pacemakers for implantation and configuring 1204 a left-ventricular
leadless cardiac pacemaker of the leadless cardiac pacemaker
plurality for implantation in electrical contact to a
left-ventricular cardiac chamber and for operation in cardiac
resynchronization therapy (CRT-D). The left-ventricular cardiac
pacemaker waits 1206 at the left-ventricular leadless cardiac
pacemaker for an earliest occurring event of a plurality of events
comprising a sensed communication of a pacing pulse marking a
heartbeat at an atrial leadless cardiac pacemaker and timeout of a
left ventricular escape interval. The left-ventricular cardiac
pacemaker responds 1208 to timeout of the left ventricular escape
interval by delivering a left ventricular pacing pulse, causing a
left ventricular heartbeat, the left ventricular pacing pulse
encoding type and location of a left ventricular heartbeat
event.
In some embodiments, the left-ventricular cardiac pacemaker can
configure the left-ventricular leadless cardiac pacemaker for
operation in cardiac resynchronization therapy (CRT-D).
FIG. 12B is a flow chart showing another embodiment of a method
1250 for operating a left-ventricular leadless cardiac pacemaker.
The left-ventricular leadless cardiac pacemaker detects 1252 a
signal originating from a co-implanted atrial leadless cardiac
pacemaker, examines 1254 the elapsed amount of the left ventricular
escape interval since a most recent left-ventricular heartbeat, and
determines 1256 whether the signal originating from the
co-implanted atrial leadless cardiac pacemaker is premature. In the
presence 1258 of a premature signal, the left-ventricular cardiac
pacemaker waits 1260 for an event with no effect on ventricular
pacing. In the absence 1262 of a premature signal, the
left-ventricular cardiac pacemaker starts 1264 a left atrium to
left ventricular (AV) escape interval that is representative of a
typical time from an atrial beat to a left ventricular beat in
sinus rhythm.
Terms "substantially", "essentially", or "approximately", that may
be used herein, relate to an industry-accepted tolerance to the
corresponding term. Such an industry-accepted tolerance ranges from
less than one percent to twenty percent and corresponds to, but is
not limited to, component values, integrated circuit process
variations, temperature variations, rise and fall times, and/or
thermal noise. The term "coupled", as may be used herein, includes
direct coupling and indirect coupling via another component,
element, circuit, or module where, for indirect coupling, the
intervening component, element, circuit, or module does not modify
the information of a signal but may adjust its current level,
voltage level, and/or power level. Inferred coupling, for example
where one element is coupled to another element by inference,
includes direct and indirect coupling between two elements in the
same manner as "coupled".
While the present disclosure describes various embodiments, these
embodiments are to be understood as illustrative and do not limit
the claim scope. Many variations, modifications, additions and
improvements of the described embodiments are possible. For
example, those having ordinary skill in the art will readily
implement the steps necessary to provide the structures and methods
disclosed herein, and will understand that the process parameters,
materials, and dimensions are given by way of example only. The
parameters, materials, and dimensions can be varied to achieve the
desired structure as well as modifications, which are within the
scope of the claims. Variations and modifications of the
embodiments disclosed herein may also be made while remaining
within the scope of the following claims. For example, although the
description has some focus on the pacemaker, system, structures,
and techniques can otherwise be applicable to other uses, for
example multi-site pacing for prevention of tachycardias in the
atria or ventricles. Phraseology and terminology employed herein
are for the purpose of the description and should not be regarded
as limiting. With respect to the description, optimum dimensional
relationships for the component parts are to include variations in
size, materials, shape, form, function and manner of operation,
assembly and use that are deemed readily apparent and obvious to
one of ordinary skill in the art and all equivalent relationships
to those illustrated in the drawings and described in the
specification are intended to be encompassed by the present
description. Therefore, the foregoing is considered as illustrative
only of the principles of structure and operation. Numerous
modifications and changes will readily occur to those of ordinary
skill in the art whereby the scope is not limited to the exact
construction and operation shown and described, and accordingly,
all suitable modifications and equivalents may be included.
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